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Scale Models Can "Compute" Casimir Forces
KentuckyFC writes "Place two conducting parallel plates a few nanometres apart and the well-known but difficult-to-measure Casimir force will push them together. The force depends crucially on the shape of the plates but nobody is exactly sure how. That's because calculations with anything other than flat plates are fiendishly difficult and measurements are even harder. Now a group at MIT has come up with an ingenious new way to investigate Casimir forces. What the team has noticed is a mathematical analogy between the Casimir force acting on microscopic bodies in a vacuum and the electromagnetic behavior of macroscopic bodies floating in a conducting fluid. Their idea is to build a centimeter-scale metal model of the system they want to investigate, place it in salt water, and bombard it with microwaves and see what happens. The team says the experiment does not measure the force on the scale model but instead a quantity that is mathematically related to the force. So the experiment is not a simulator but actually an analog computer that calculates the force (abstract). What's exciting is that the method should for the first time give researchers a way of testing nano-machines designed to exploit the Casimir force."
No. They know the mathematics behind the system, however, they cannot solve the equations directly. What they have done is taken a system that works according to the same equations. Knowing how this system responds means that you can also work out how the first system responds. Easy.
[FUCK BETA]
Good explanation.
An oft-used classical analogy is of boats on a wavy sea. It's been reported that two ships sitting on a wavy sea (but windless day) will slowly move closer together, as if they are 'attracted' to one another. The origin of the force is the waves of various wavelengths that form on the water surface. The sea surface has waves of all different sizes. In between the two ships, however, some wavelengths can't 'fit' and so those modes are suppressed. The end result is that there are fewer wave between the ships, so the greater pressure from the (more) waves on the other sides of the ships pushes them closer together. (I'm glossing over the details, e.g. that you have to take into account how the waves on the surface of the sea reflect off the ship's hulls... but hopefully you get the idea.)
The Casimir force is like the quantum version of this. According to quantum mechanics, the vacuum is constantly churning with the creation and annihilation of virtual particles. Thus there are quantum waves of all kinds of different wavelengths. In between two plates, some quantized modes can't exist, and are suppressed. The end result is that there is more pressure from the vacuum on the outside of the plates than in the gap between them. Hence the plates are pushed together by the vacuum pressure.
Note that in both cases the magnitude of the force is quite small, and so you have to be quite careful to observe the force and measure it properly.
I like it as it reminds me of Archimedes. If you can't compute the volume , stick it in a tub of water and do an atomic integral of the volume.
Also I didn't see the meme so I have to do this,
But will it run Linux?